1. Field of the Invention
The present invention relates to a lithographic printing press and more particularly to a supplementary liquid dispensing device for a dampening or moistening system in a lithographic printing press. While the present invention may be utilized in other dampening and moistening systems, the supplementary liquid dispensing device of the present invention is particularly useful in a dampening or moistening system utilizing alcohol as a wetting agent.
2. Prior Art
Dampening or moistening systems for lithographic presses are well known to those skilled in the art. Basically, in such systems, liquid distributing rollers are rotated by friction or by mechanical drives to transfer a dampening agent or fountain solution from an open tray containing the fountain solution to a plate cylinder of the lithographic printing press. A fountain roller revolves in the fountain solution and transfers the fountain liquid to a ductor roller. Some known dampening systems to which the present invention may be used are the Molleton Dampener and the Aquamatic System of an A. B. Dick offset press manufactured by the A. B. Dick Co. It should be understood, of course, that the supplementary liquid dispensing device of the present invention may be utilized in other dampening or moistening systems. In such systems, one of the problems is that the open tray permits evaporization of the alcohol wetting agent in the fountain solution to the atmosphere or ambient air. In the past sophisticated, complex and expensive electronic systems were utilized to maintain the alcohol contents in the fountain solution at a certain level or a given specific gravity. Such systems generally were responsive to the specific gravity of the fountain solution and attempts were made to maintain the proper specific gravity of the fountain solution by adding alcohol to the fountain solution as the specific gravity of the fountain solution changed. Such systems are disclosed in U.S. Pat. No. 3,485,257 to H. W. Gegenheimer et al, entitled "Fountain Solution System and Apparatus Therefor"; U.S. Pat. No. 3,557,817 to Edwin H. Royse, entitled "Control for Mixing Fluids of Different Specific Gravity"; and U.S. Pat. No. 3,947,356 to Alfons Werhli, entitled "Arrangement for Regulating the Moistening Solution Mixture in a Moistening Solution Preparation Plant for an Offset Printing Press". Other attempts were to manually pour alcohol into the fountain solution, which of course, was left to the discretion of the press operator, and generally the pouring of the alcohol into the fountain solution by the operator was not in uniform intervals of time or quantity. Accordingly, some of the accompanying problems resulted in that the specific gravity and pH(Hydrogen ion concentration) of the fountain solution changed radically before and after pouring alcohol. Thus, the alcohol wetting agent variation resulted in polluting the non-image forming areas and emulsification of the ink due to the variation of the specific gravity and pH of the fountain solution.
This problem is especially significant when the pressroom temperature is particularly high since alcohol will evaporate from the fountain solution at a relatively high rate, thus creating the problem of maintaining the lithographic printing at a high level of quality.
Accordingly, there is a pressing need for a relatively simple, inexpensive, efficient supplementary liquid dispensing device for a dampening system of a lithographic printing press to maintain the alcohol content, the specific gravity and pH of the fountain solution of the dampening system at a reasonably constant level to insure quality printing. It is also necessary that any device for adding alcohol in and ofitself does not contribute to air polution by direct evaporization of the alcohol to the atmosphere. These problems are multiplied in a multicolor, lithographic printing system where multiple dampening systems are employed.